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Appendix A. — Kelative Values of various Units of Electrical Eesistance. 



Description. 



Weber's: 



Siemens 

 (London). 



Digney. 



Varley. 



Becond 

 inits (new determination) 

 foot ..,„.,. 



Twenty-five feet of a certain cop- ' 

 per wire, weighing 345 grains . . . 



^IlxlO'electro-mag- 

 second 

 netic units determined by Weber 



Absolute r- 



socond 



Thomson's unit 



(18(12). 



One metre of pure mercury, one 



square millimetre section at 0° C. 



One metre of pure mercury, one 



square millimetre section at 0° 0. . 



second 



xio' 



Siemens 1864 issue.. 

 Siemens (Berlin) . . 

 Siemens (London) . . 



British Association unit 



One kilometre of iron wire, four 

 millimetres in diameter (tempe- 

 rature not known) 



One kilometre of iron wire, four 

 millimetres in diameter (tempe- 

 rature not known) 



One kilometre of iron wire, four 

 millimetres in diameter (tempe- 

 rature not known) 



One English standard mile of pure " 

 annealed copper wire -Jj. in. dia- • 



. A. unit, or Ohmad. 



One English standard mile of one 

 special copper wire ■& inch in 

 diameter 



One German mile=8238 yards of 

 iron wire £ inch in diameter 

 (temperature not known*) 



Digney 



Brequet 



Swiss 



Matthiessen.. 



Varley 



German mile 



I -000 

 1-0505 



34-21 

 44-57 

 8401 



188-4 



0-9520 

 1-000. 



2-988 

 3004 



32-56 

 42-43 

 79-96 

 1794 



21-34 

 40-21 



0-3316 

 0-3483 



10-62 

 11-34 



14-78 

 27-85 



1-000 

 1-005 

 1-017 

 1-0456 



00968 

 10-20 

 10-90 

 1419 

 26-75 



10-15 

 10-84 

 1412 

 26-61 

 59-71 



0-3131 



0-9881 

 1-000 

 1026 



9-520 

 1013 

 10-71 

 13-95 

 26-30 



01038 

 01050 



01079 



1-000 

 1-054 

 1-125 



0-09177 

 0-09227 



1-000 

 1-303 

 2-456 

 5-509 



007047 

 0-07081 

 007166 

 00736 

 0-6822 

 0-7187 

 0-7675 



001190 

 001251 

 0-02486 



003737 

 0-03757 



0-3814 

 0-4072 

 0-5306 

 1000 

 2-243 



0005307 

 0-005574 

 9-01108 



001666 

 001675 

 0-01695 

 001741 



0-1613 

 01700 

 0-1815 

 0-2365 



0-4457 

 1-000 



Calculated from the B. A. unit. 



iYo measurement made; ratio be- 

 tween Siemens (Berlin) and .la- 

 cobi taken from "Weber's Gal- 



Measurement, taken from a deter- 

 mination in 18112 of a standard 

 sent by Prof. Thomson ; docs not 

 agree uilb Weber's own mei 

 ment of Sieineus's units ; by We- 

 ber 1 Siemens's unit = 1 -025 X 10' 

 metres-second. 

 I Measurement taken from threecoils 

 | issued by Messrs. Siemens. 



{Measurement taken from coils exb 

 bited in 1862 by Messrs. Siemens 

 Halske & Co. (well adjusted), 

 r Measurement taken from coils exhi 

 1 bited in 18(12 by Messrs. Siemens. 

 [ Halske & Co. (well adjusted). 

 f Equal to 10,000,000 ^^ no 

 | cording to experiments of Stand 

 \_ ard Committee, 

 f From coils exhibited in 18C2 (prett< 

 \ well adjusted). 



f From coils exhibited in 1862 (in 

 \ differently adjusted). 



/From coils exhibited in 1862(badlj 

 \ adjusted). 



i (of German-i 



J From coils lent by Mr. Varley (well 

 adjusted). 



Messrs. 



Siemens do not now manufacture coils with this unit, which has been abandoned by them in favour of the mercury unit given above. 



